The present invention relates to an anti-reflective coating composition, and more particularly, to an anti-reflective coating composition having adhesive properties with respect to a photoresist film and a substrate.
A main component of a photoresist is a photosensitive polymer which is solubilized or insolubilized by irradiation. The photosensitive polymer is a hydrophobic organic material and, accordingly, exhibits poor adhesion to a hydrophilic material. Coating photoresist on a relatively hydrophilic substrate often leads to poor adhesion. Therefore, poor photoresist adhesion leads to undercutting, reduced resolution or, in extreme cases, total pattern destruction. Furthermore, poor adhesion increases the possibility of the photoresist lifting off from the substrate during subsequent processing (e.g., etching), whereby the developed image is incorrect.
A method for enhancing the adhesion of a photoresist to a substrate, wherein a surface of a substrate has been treated with an organo-silane compound having a bulky hydrocarbon group, has been proposed. The most representative method for enhancing adhesion of a photoresist is to use hexamethyldisilazane (HMDS) which is an organo-silicon compound, as an adhesion promoter. The HMDS causes bonding of silicon atoms and oxygen atoms in the substrate, thereby changing the surface from hydrophilic to hydrophobic.
Meanwhile, uneven topology is a serious problem in photolithography processes, since it causes diffused reflection leading to photoresist notching. To prevent the notching of a photoresist, there is a method wherein reflected light is absorbed by using a material having light absorbing properties at a wavelength region of a light source used in the photolithography processing. That is, a compound absorbing 436 nm (g-line) or 365 nm (i-line) light absorbs the reflected light, which prevents light-induced change of a photo-active compound in the photoresist.
Ways for using such light absorbing material includes the following two methods: one method wherein a dye is added directly to a photoresist or another method wherein a dye or a particular wavelength absorbing compound is coated on a photoresist or a substrate. The particular photoresist added with dyes has an enough high light absorption coefficient to absorb reflected light. Accordingly a photo-active compound in a non-exposure portion is protected so that it does not react to reflected light. However, the method of adding dyes does require increased light exposure. Therefore, the recent trend is to use an anti-reflective coating for preventing photoresist notching. Widely used as the anti-reflective coating is a water-soluble material including a chemical material for a dyestuff which can maximally absorb light at a particular wavelength region. Meanwhile, according to the above dye coating method, a thin anti-reflective coating of about 50 nm can be obtained by coating and dying dyestuff material a substrate or photoresist.
Further, to improve adhesion of the photoresist and present the phenomenon of notching, due to diffused reflection, an adhesion promoter such as HMDS and a light absorbent, such as dye had to be used, which led to increased manufacturing cost of semiconductor devices.